Serum vitamin B₁₂ concentrations and atrophic gastritis in older New Zealanders

Objective: To determine the serum vitamin B₁₂ status of older New Zealanders and to assess the impact of atrophic gastritis on vitamin B₁₂ status. Design: A cross-sectional nationally representative population-based survey. Method: Serum vitamin B₁₂ concentrations were used to assess vitamin B₁₂ status. The presence and severity of atrophic gastritis was classified using serum pepsinogen I and II. Subjects: A total of 466 noninstitutionalized urban and rural dwelling New Zealanders aged 65y or older who participated in the 1997 National Nutrition Survey. Results: The prevalence of deficient (<148 pmol/l) and marginal (148-221 pmol/l) serum vitamin B₁₂ concentrations was 12 and 28%, respectively. The prevalence of atrophic gastritis was 6.7% (severe 3.1%, mild-moderate 3.6%). While atrophic gastritis increased the relative risk (RR, 95% CI) of having a deficient or marginal serum vitamin B₁₂ concentration by 21-fold (6-67) and five-fold (1-17), respectively, those who had atrophic gastritis made up only 33 and 6% of the participants with deficient or marginal serum vitamin B₁₂ concentrations. An intake of vitamin B₁₂ from food that exceeded the recommended dietary allowance (2.4 μg/day) did not protect against deficient (RR 0.5; 95% CI: 0.2, 1.2) or marginal (RR 0.9; 95% CI: 0.5, 1.7) serum vitamin B₁₂ status. Vitamin B₁₂ supplement users had a reduced risk of having deficient and marginal vitamin B₁₂ status (RR 0.3; 95% CI: 0.1, 0.8). Conclusions: There is a relatively high prevalence of deficient and marginal serum vitamin B₁₂ concentrations among older New Zealanders. However, the prevalence of atrophic gastritis was low in the New Zealand elderly compared with other surveys. Although atrophic gastritis was a risk factor for low vitamin B₁₂ status, it did not fully explain the prevalence of low serum vitamin B₁₂.